Method of and apparatus for producing dried whole eggs



Oct. 16, 1951 W, N, LINDSAY ETAL 2,571,459

METHOD OF' AND APPARATUS FOR PRODUCING DRIED WHOLE EGGS Oct. 16, 1951 w. N LINDSAY ET Al.

METHOD OF' AND APPARATUS FOR PRODUCING DRIED WHOLE EGGS 15 Sheets-Sheet 2 Filed NOV. 5, 1945 MIN Oct. 16, 1951 w. N. LINDSAY ET Al.

METHOD OF AND APPARATUS FOR PROOUOING DRIED WHOLE EGGS 1s shee' -Sheet 3 im. OWN a .NW

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Oct- 15, 1951 w. N. LINDSAY ET AL' 2,571,459

METHOD OF AND APPARATUS FOR PRODUCING DRIED WHOLE EGGS Filed Nv. 5, 1945 15 Sheets-Sheet 4 Ffa 5.

Oct. 16, 1951 w. N. LINDSAY ETAL 2,571,459

METHOD OF ANO APPARATUS FOR PROOUCING DRIED WHOLE EGGS Filed Nov. 5, 1945 13 Sheets-Sheet 5 ATTONEY 00L 16, 1951 w. N.L.|NDsAY ET AL 2,571,459

METHOD OF' AND APPARATUS FOR PRODUCING DRIED WHOLE EGGSv Filed NOV. 5, 1945 13 Sheets-Sheet 6 /NVfA/MQJ; ff@ Z Wfufy M maf/ly Oct. 16, 1951 METHOD OF AND APPARATUS F'OR PRODUCING DRIED WHOLE EGGS Filed NOV. 5, 1945 13 Sheets-Sheet '7 Oct. 16, 1951 w. N. LINDSAY ETAL 2,571,459

lMEII-IOD OF' AND APPARATUS FOR PRODUCING DRIED WHOLE EGGS Filed'Nov. 5, 1945 13 Sheets--Sheerl 8 ,g S l, v Q :s

Oct. 16, 1951 w. N. LINDSAY ETAL 2,571,459

METHOD OF AND APPARATUS FOR PROOUCING DRIED WHOLE EGGS Filed Nov. 5, 1945y 15 sheets-sheet s /A/z/f/vroxan Wawy N uur Oct. 16, 1951 w. N..L|NDsAY ETAL 2,571,459

METHOD oF AND APPARATUS FOR PRODUCING DRIED WHOLE EGGS Filed Nov. 5, 1945 15 shets-sheet 1o wFm f5 Oct. 16, 1951 w. N. LINDSAY ETAL METHOD OF AND APPARATUS' FOR PRODUCING DRIED WHOLE EGGS 13 Sheets-Sheetll Filed NOV. 5, 1945 06f. 16, 1951 W N, LlNDsAY ETAL 2,571,459

METHOD OF' AND APPARATUS FOR PRODUCING DRIED WHOLE EGGS Filed. Nov. 5, 1945 13 Sheets-Sheet l2 Oct 16, 1951 w. N. LINDSAY ETAL 2,571,459

METHOD oF AND APPARATUS FOR PRonucING DRIED WHOLE EGGS Filed Nov. 5, 1945 15 sheets-sheet 1:5

Pafented oct. 16, 195i BIETHOD F AND APPARATUS FOR PRO- DUCING DRIED WHOLE EGGS Wesley N. Lindsay and Paul C. Wilbur, San Jose,

Calif., assignors to Food Machinery and Chemical Corporation, a corporation of Delaware Application November 5, 1945, Serial No. 626,826

(Cl. 15S- 48) 8 Claims.

'I'his invention relates to the art of preparing liquid foods in powder form. Although the invention has wide utility and can be used in reducing various liquid foods to powder form, it is especially adapted for the production of low moisture dried whole egg and for illustrative purposes will be so disclosed herein.

The production of powdered eggs commercially has for long been carried on by rst breaking the eggs, separating the shell from the meat and after 'mixing the whites and yolks to produce liquid whole egg meat, spraying this into stream of hot air discharged into a large chamber. The particles ,into which the egg is divided by the spraying action are dried solid by the air, after which the; fall into the bottom of the spray chamber in the form oi' powder or collect on fabric bags through which the air escapes. This is known/as the spray method, and prior to the development of the present invention, produced practically all of the powdered egg sold cornmercially.

- This product is customarily packed in cans, cartons or barrels without being sealed from the atmosphere. Prior to this invention, the greatest demand for powdered eggs came from bakeries. Powdered eggs may be reconstituted as liquid whole eggs by the addition of water and cooked much the same as fresh eggs in the form of scrambled eggs or omelets and the like and have a similar appearance to fresh eggs when thus 'are kept more than a few months before using or where these are subjected to high atmospheric temperatures as in tropical climate.

As the result of this tendency of powdered egg as hitherto produced commercially to deteriorate, it has not been practicable to rely upon it for use in cooking various dishessuch as scrambled eggs and omelets and the possible market for eggs in powdered form has thus4 been greatly limited.

It is an object of this invention 4to provide a method of and apparatus for manufacturing dried whole egg, the keeping qualities and continued palatability of which may be relied upon so as to greatly increase the opportunities for sale and consumption of this product.

There are several factors determining the stability of egg powder. The most important of these is the moisture content ofthe powder which is ordinarily measured in percent by weight of water. Another factor is the temperature at which the powder is stored. Still another is the presence in the egg powder of bacterial enzymes derived from bacterial activity in the original liquid eggs. The opportunity for the latter two factors to bring about a deterioration in the quality of egg powder is lacking, however, in proportion to the degree to which the moisture content of the powder is reduced.

It is accordingly an important object of this invention to provide a method of and apparatus for manufacturing dried whole egg powder with a relatively low moisture content.

Reconstituted liquid whole egg approaches fresh l liquid whole egg in quality in proportion as the egg powder from which it is made is soluble in water and is free from elements oiensive to the senses of taste and smell. Thus egg powder is not only tested for moisture content to determine its stability in resisting deterioration, but it is also tested for solubility, and for fluorescence, the latter being an index of elements in the powder which tend to impair its palatability.

In producing egg powder from liquid Whole egg, the palatability and solubility of the latter may easily be impaired by heat damage incurred in the drying process. Attempts to reduce the moisture content of egg powder to a low point by previous methods have resulted in serious decreases in solubility and increases in fluorescence values.

It is a further object of this invention to provide a method of and apparatus for producing an egg powder of low moisture content, or high solubility, and with a low uorescence value.

Previous eiorts to produce a whole egg powder with relatively low moisture content have been mainly along the lines of increasing the temperature of the air in the spray drier, or of resuspending the powder particles in a stream of dry hotl air. These methods have had only a relatively small measure of success due to the fact that the egg powder would become scorched and its palatability impaired whenever temperatures and time periods were employed which were necessary to attain the desired low moisture content.

It appeared to us that this scorching takes place when the egg particles are heated to approximately the temperature of the drying air while these particles are still relatively moist. We conceived, therefore that the desired low moisture content could be attained in whole egg powder if the particles thereof could be subjected to dry air of the required high temperature for the necessary time period without permitting the temperature of these particles to be raised to approximately the temperature of the air, and to prevent this particularly, while the particles are still relatively moist.

It is a still further object of this invention to provide a method of and apparatus for producing commercially, an egg powder of low moisture content in which air of relatively high temperature may be applied to the whole egg particles without heating these particles to approximately the temperature of said air while said particles are relatively moist.

The method of this invention starts with an initial drying step in which the liquid whole egg meat is reduced, as by the spray method, to a relatively high moisture powder. The balance of the method involves further reducing the moisture content of this powder without damaging it.

Other liquid foods such as milk and pureed soups are also commonly reduced commercially to powder form by the spray method. These powders are organic and hygroscopic and the drying of these present problems similar to those met in producing dried while egg. It is thus clear that this invention is adaptable to the redrying of various liquid foods capable of reduction to hygroscopic powders although it is particularly useful in producing low moisture dried egg powder having exceptional qualities of palatability and resistance to deterioration.

It is therefore a broad object of this invention to provide a method of and apparatus for redrying hygroscopic, organic powders produced in the first instance by drying liquid foods.

The manner of accomplishing the foregoing objects, as well as further objects and advantages will be made manifest in the following description taken together with the accompanying drawings in which:

Fig. l is a diagrammatic perspective view of a preferred embodiment of the apparatus of the invention.

Fig. 2 is a diagrammatic elevational view ofthe drive mechanism of said apparatus.

Fig. 3 is a diagrammatic enlarged horizontal sectional view taken on the line 3-3 of Fig. 1.

Fig. 4 is a diagrammatic vertical longitudinal sectional view taken on the line 4-4 of Fig. 3.

Fig. 5 is an enlarged side elevational view of the left half of said apparatus `with the side panels thereof removed and partially broken away to illustrate hidden portions of the mechanism.

Fig. 6 is a corresponding side elevational view of the right half of said apparatus.

Fig. '7 is a view taken on the line 1--1 of Fig. 6 with parts of the apparatus broken away to reveal the structure of normally hidden portions thereof.

Fig. 8 is a cross-sectional view similar to Fig. 'l and taken on the line 8-8 of Figs. 3 and 5.

Fig. 9 is an enlarged fragmentary cross-sectional view taken on the line 9-9 of Fig. 6 and illustrating the powder valve through which powder is introduced from the drying chamber of the apparatus into the powder cooler.

Fig. l0 is an enlarged plan view of an end portion of one of the cross bars of the drying belt supporting apron of the apparatus.

Fig. 11 is a cross-sectional view taken on the line lI--II of Fig. l0.

Fig. 12 is a diagrammatic perspective view of the cooler and air handling devices of the apparatus of the invention.

Fig. 13 is a fragmentary perspective view of the drying belt tightener of the apparatus.

Fig. 14 is an enlarged cross-sectional view taken on the line |4-I4 of Fig. 13. l

Fig. 15 is an enlarged sectional view taken on the line lB--IS of Fig. 13.

Fig. 16 is a diagrammatic fragmentary plan view of the drying belt centralizing mechanism of the invention.

Fig. 17 is a side elevational view of Fig. 16.

Fig. 18 is an enlarged cross-sectional view taken on the line |8--Il of Fig. 17.

Fig. 19 is an enlarged cross-sectional view taken on the line I9-l9 of Fig. 17.

Referring specifically to the drawings andv in may be designated generally by the numeral 25. This includes a liquid egg spray drier 26 and an egg powder drier 21. l

Being of a well known type in common use prior to this invention, the spray drier 26 will not be disclosed herein in detail. It comprises a cyclone-like shell 30 in the shape of an inverted pyramid. At its lower end this terminates in a sump 3|. Opening upwardly from the shell 30 is an air outlet 32.

A spray manifold 3l leads to suitable nozzles (not shown) which are located inside the shell III. Liquid egg is supplied under pressure to the manifold 33 and discharged from said nozzles into the interior of the shell 30 in the form of ilne spray. A hot air manifold 35 delivers hot air into the interior -of the shell 30 `in blasts which are concentric with said nozzles. This air is delivered at a temperature of about 20G-235 F. and in sufficient volume to evaporate the moisture from the liquid egg particles delivered from the spray nozzles so that these gravitate into the sump 3l of the drier 26 in the form of a powder. Extending into the sump 3i for removing powder therefrom as this accumulates is a screw conveyor elevator 36.

The powder drier 21 has a frame 50 including a base 5i (Fig. 6) formed of structural steel and a rectangular super structure 52 `of the same material. This super structure supports bottom side panels 5I (Fig. 8) which are preferably formed of only a single thickness of sheet metal, upper side panelsjl which are double walled and filled with insulating material, similar insulating end panels 55 and 56 (Figs. 4, 5 and 6), a similar but thicker insulating top wall 58 (Figs. 4, 5, 6, 7 and 8), and a bottom wall 58 of similar insulating construction, portions 60 and 6| of which are joined by a vertical portion 62 (Fig. 4).

The panels 5I, 55, 56, and the top wall 58 and bottom wall 59 are thus seen to unite to form an insulated housing 65 enclosing a drying chamber 66 (Figs. 3, 4,5, 6, l and 8).

Mounted on U-shaped channel members 10 and 1I which are embodied in the frame 50 and extend upwardly into the chamber 66, is a continuous powder bank forming and drying mechanism 12 (Fig. 4). This includes a suction box 1I, end walls 14 of which are secured to the members 10 and 1I at the back side of the drier.

' 'I'hrough this connection, the box 13 and the '(5 downwardly from their inner edges (Fig. 8). Ex-

5 tending inwardly from the upper edges of end walls 14 (Fig. 4) are similar edge plates 8| which unite with the plates 19 to form a frame about a central suction opening 82 in the top of the box 13. Secured to box side walls 16 and 11 (Figs. 4 and 8) and extending across the box are channel members 85 which support apron support channel members 86. Formed in the central partition 18 (Fig. 4) are upper and lower openings 81 and 88 respectively, the purpose of which will be made clear hereinafter. Supported by the partition 18 and the right end wall 14 adjacent opposite ends of opening 88 are apron supporting angle members 89 (Figs. 4 and 8).

The opening 81 (Fig. 4) is formed in the upper edge of the central partition 18 and is provided with a dared horizontal guide plate 90 along its horizontal edge. Similar guide plates 9| are provided along the upper and lower Vhorizbntal edges of the opening 88.

Formed in the side wall 11 on one side of the partition 18 is a suction hole 92 while a similar hole 93 is provided in said wall on the opposite side of the partition 18.

Mounted in the box 13 so that the upper flight thereof is level with the edge plates 19 and 8| and substantially iills the central suction opening 82 of this box lis a traveling apron 94 (Figs. 4, 7 and 8). This is supported on driven and drive shafts 95 and 96 (Fig. 4) respectively which journal in suitable bearings 91 and 98 which are provided on box side walls 16 and 11. These shafts have spaced pairs of sprockets 99 about which are trained chains |08. These chains are made up of attachment links, to corresponding opposite pairs of which are attached U-shaped sheet metal cross bars |05 (Figs. 4, 8, 10 and 11).

These cross bars are preferably formed of sheet metal re-bent to provide a heavy base |06 having a pair of holes |81 through which bolts may be received to secure the bar to the attachment links of the chain |08. lFormed by upwardly bending this metal on one edge of this base |06 is a vertical wall |08. Bent from the upper edge of this is a top wall |09, an edge flange ||8 of this being bent down for strengthening purposes. The top wall |09 of the .bar |05 is provided with a multiplicity of perforations Those portions of chains disposed in the upper flight of the apron 94 rest on and are guided by the apron supporting channel members 86 (Figs. 4 and 8). While disposed in this upper ight, the cross bars of said apron are substantially in contact with each other to present a practically continuous perforated surface throughout all portions of the central suction opening82 of the suction box 13.

The openings 88 and 81 and the guide plates 90 and 9| bordering these are shaped to conform closely to the upper and lower flights of the endless apron 94 as these pass through these openings. Thus the partition 18 makes a fairly tight wall dividing opposite end portions of the suction box 13 so that this box includes a primary suction chamber I6 and a secondary suction chamber ||1 (Fig. 4).

The side walls 16 and 11 have end extensions ||8 and ||9 just within the housing end 56 (Figs. 3 and 7). Provided on the frame 58 is a bearing support plate |20 which is coextensive with and disposed opposite the wall extension ||9 and in spaced relation therewith. Disposed between the wall extensions ||8 and ||9 (Figs. 4 and 7) are upper and lower drier belt drive pulleys |2| and |22 and a beater roller |23,

beater flanges |24 being provided on the latter.

The pulleys |2| and |22 have suitable trunnions that the drive shaft 96 of the endless apron 94 has a large diameter sprocket |40 which lies in the same plane as the sprockets |33 and |34 and with the drive sprocket |4| of a geared electric motor |42, these sprockets all being connected by a drive chain |43 trained thereabout.

The beater roller |23 is driven by a motor |44 having a pulley |45 which lies in the same plane as pulley |35 and is connected thereto by a drive belt |46.

Formed on the suction box side walls 16 and 11 (Fig. 8) and extending therefrom towards the housing end wall 55 (Fig. 4) is a pair of vertical plates |41, these plates carrying pairs of bearings |48 and 4|49 (Fig. 5) in which are journaled suitable trunnions provided on opposite ends of idle drier belt pulleys |50 and |5| (Fig. 4). Extending inwardly from lower ends of the vertical plates |41 (Figs. 5, 16 and 17) are arms |52 which are rigidly spaced by a spacer |53.

Mounted on the arms |52 is a drier belt equalizing device |54 (Fig. 16). This device includes angle members |55 which are secured as by welding to outside faces of the arm |52. These angle members have horizontal flanges |56'which are slotted longitudinally to receive cap screws |51 which adjustably secure upper and lower trunnion plates |58 to the members 55. Secured as by welding to the fianges |56 are blocks |59 having set screw |60 which bear against plates |58 and provide adjustable stops for these plates.

Mounted between the spaced ends of the trunnion plates |58 are bearing cradles |6| (Fig. 17)

each of which comprise a U-shaped yoke |62` including parallel arms |63 and a connecting back bar |64. Secured to inner faces of the arms |63 are bearing mounting plates |65. Formed in each pair of trunnion plates |58 are vertically aligned holes |10 (Fig. 18) which receive pins |1| on inner ends of which are provided ball bearings |12 which are snugly received in holes |13 provided in the yoke arms |63. Offset outwardly from the axis of the bearings |12 are holes |14 formed in the plates |65. These holes contain bearings |15 which receive pins |16, the latter extending into recesses |'11 provided in a. pulley bearing |18. This bearing may be provided with a sleeve |19 and have its outer end covered by a cap |80.

Disposed between the bearings |18 of the equalizer |54 is an equalizing drier belt pulley |8| (Fig. 16) having trunnions |82 (Fig. 18) at its opposite ends which journal `in these bearings.

Fixed to the back bar |64 of each yoke |62 is a. control arm |86 (Figs. 16 and 17).

The outer ends of the arms |86 are pivotally connected by ball bearings |81 (Fig... 11) to opposite ends of an angle cross arm |88 (Fig. 16). The arms |86 are thus tied together, yet permitted a limited degree of swinging movement about the pins |1|. Each of the bearing yokes 7 partakes of this swinsing movement of the arm |96 to which it is rigidly secured.

Adjustably secured in slots |99 provided in the cross arm |00 are pin bolts |90 (Figs. 16 and 19) on the lower ends of which are provided ball bearings |9| on which rollers |92 are rotatably supported.

Mounted on the housing lower wall 59 is a drier belt tightener 200 (Figs. 4, 5, 6 and 13). This comprises a tightener pulley 20|, opposite ends of which are pivotally mounted on corresponding ends of a pair of horizontal bars 202 which extend through holes 203 (Fig. 4) in the vertical portion 62 of the bottom wall 59 of the housing so that the pulley 20| is within the drying chamber 66. Mounted on the vertical wall portion 62 are rollers 204 which support the bars 202 so that they readily slide in the openings 203. Secured to the bars 202 by bolts 201 are racks 200, the bolts 201 extending through slots 209 in these racks to provide for longitudinal adjustment of the latter on the bars 202. The racks 200 extend beyond the outer ends of the bars 202 and have screw blocks 2|0 in which adjustment screws 2|| are provided to bear against adjacent ends of the bars 20'2 to effect small adjustments in the longitudinal relationships of the racks 209 and the bars 202. The bolts 201 are of course loosened to permit such adjustments and are thereafter tightened.

Mounted on the horizontal bottom housing wall portion 6| (Figs. 4 and 5) just inside of the bars 202 are bearing plates 2I'5. These carry flanged rollers 2| 6 on which the racks 208 ride and also provide bearings for a shaft 2|1 having fixed thereon pinion gears 2|0 which mesh with the racks '209. Fixed on the front end of the shaft 2|1 is a handle 2|9. Also fixed to the shaft between the plates 2|5 is a sleeve drum 220 on which a cable 22| is coiled, the free end of this having a weight 222 suspended thereon. This weight tends to rotate the shaft 2|1 to extend the bars 20'2 inwardly through the openings 203.

The structure described hereinabove is so made that an endless canvas drier belt 230 (Fig. 4) may be inserted into place so as to surround the suction box 13 and be trained about the pulleys |2|, |22, 20|, |0|, |5|,and |50 as shown inFigs. 3 and 4. To accomplish this, the front side panels 54 (those disposed toward the left in Figs. '1 and 8) are removed so that the powder drier 21 appears as shown in Figs. 5 and 6. Before the belt 230 may be thus inserted, jacks 23| and 232 which are provided between the lower edge of the suction box side wall 16 and the housing bottom wall portion 6| are removed temporarily.

When first inserting the belt 230, tightener pulley A20| is shifted as far as it will go to the right (as viewed in Fig. 4) by manual rotation of the shaft 2|1. When the belt 230 has thus been inserted and properly centralized in the machine, the handle 2|1 is released permitting the weight 222 to shift the pulley 20| against the belt 230 and thus tighten this. The desired degree of tightness is thus maintained in the belt in accordance with the size of the weight 222 which is applied to the cable 22| (Fig. 13).

As may be noted from Figs. 3, 4, and 8, the upper flight of the belt 200 overlies the suction box 10 and covers the suction opening 02 and the upper flight of the apron 94 which is disposed in this opening. The belt 230 is also wide enough to overlap the marginal top plates 19 about 6 inches on each side of the suction opening 82.

The belt centralizer |54 (Fig. 17') serves to keep the belt 290 centralized with respect to the pulleys about which it is entrained and thus prevent it straying more than a slight amount away from its centralized position in the machine.

This correction is effected by the positioning of the rollers |92 (Fig. 16) in contact with opposite side edges of the belt 230. Thus when the belt starts to stray to one side or the other, it shifts one of these rollers which swings the arms |00 and the bearing cradles |6| in the same direction about their respective pins |1|. Any such movement shifts the bearings |16, in which opposite ends of the pulley |0| journal, horizontally in opposite directions, thus cooking the pulley |0| a slight amount and in the proper direction to cause the belt to shift back towards the center from the side towards which it had strayed. By means of adjustment of the roller supporting bolts |90 in the slots |09 (Fig. 16) the belt centralizer |54 may be caused to maintain the belt centralized regardless of occasional unequal stretching of opposite edge portions of the belt.

Associated with and adapted to supply dry, hot air, or any other suitable gas, to the powderbank forming and drying mechanism 12 (Fig. 4) is the air drying and circulating mechanism 240 (Figs. 1 and 12). Embraced in this mechanism is a silica-gel air drier 24| (Fig. 1) having an inlet pipe 242 and an outlet pipe 243. This drier may be of any suitable type, and a Bryant rotary dehumidifier, model 29-R, made by the Bryant Heater Company of Cleveland, Ohio has been found to satisfactorily perform the function of the air drier 24|. The Bryant rotary dehumidifier is thoroughly illustrated and described in a catalogue published by the Bryant Company in April 1943, and includes one or more rotary double walled screen-drums, the space between the two screens being packed with silica-gel. Each such rotating drum is confined within a housing which is divided, by partitions extending longitudinally of and disposed within and outside of said drum, into two chambers-a reactivating chamber and an air drying chamber. In the first chamber, the silica-gel is heated to reactivate the same and in the second chamber, wet air is passed through the silica-gel to remove the moisture from the air.

The mechanism 240 also includes primary and secondary air heaters 260 and 26| having air discharge risers 262 and 263; an air cooler 264; and primary and secondary air blowers 265 and 260.

As shown in Fig. 12, the heaters 260 and 26|, the cooler 264, and the blowers 265 and 206 are mounted on the base 5| of the powder drier frame 00. The dry air discharge pipe 249 of the air redrier 24| connects with and discharges vsuction end of the blower 265.

Leading from the discharge end of this blower to the heater 26| is a pipe 210. This pipe extends beyond the heater 26| and then returns to the latter to provide a sufficiently long, straight section in this pipe in which to place a flow meter (not shown).

The air thus delivered to the heater 26| is heated therein and then discharged upwardly from the riser 263 into the drying chamber 66 (Figs. 3, 4, land 8). Secured to the upper edge of the suction box side wall 11'and extending horizontally therefrom to close the space which surrounds the riser 263 between this wall and the housing side wall 54 is a plate 21| (Fig. 3).

Mounted in the space between the housing top wall 58 and the drier belt 230 to substantially prevent mixing of` air discharged upwardly from the risers/262 and 263 is a central baille wall 212 (Fig. 4) which has a long narrow recess 213 at its lower edge to accommodate the passage therethrough of a bank of powdered egg carried on the drying belt 230.

Connecting with the suction opening 93 in the suction chamber ||6 (Figs. 4, 8 and 12) is a relatively flat conduit 218 which is connected to the cooler 264 by a pipe 219. This cooler cools air passing therethrough which is sucked therefrom by a pipe 280 connecting the cooler to the suction end of the blower 266. This air is then delivered from the discharge end of the blower 266 to the pipe 242 through which it is returned to the air redrier 24|.

Egg powder producedI in the spray drier 26 (Fig. l) is received from the conveyor 36 and delivered onto the drier belt 230 of the powder drier 21 by a powder feeder 28| (Figs. 1, 4, 5 and '7) This feeder is mounted on the drier top wall l 58 and includes a mixing trough 282 which is closed by a cover 263 having an inlet pipe 288 through which powder is delivered from the conveyor 36 into one end of the trough 282. Journailed in suitable bearings 285 and 286 (Fig. 8) provided on opposite ends of the trough 282 is a shaft 281 which carries helically inclined paddles 288 at spaced intervals throughout its length, and scoop paddles 289 at the opposite end of the shaft from the inlet pipe 284. The shaft 281 is rotated slowly through a suitable transmission 290 by a motor 29| so that the paddles 288 cause the powder delivered through the pipe 284 to progress towards the opposite end of the trough I82 until, after being thus thoroughly mixed, it is delivered to the scoop e paddles 289.

Extending into the trough 282 within the sweep of the scoop paddles 269 (Fig. 7) is a powder receiving hopper 295 which connects with a pipe 296, the latter extending downwardly through the housing top wall 58 (Figs. 4 and 8) A guide wall 291 (Fig. 4) guides into the hopper 295, powder lifted by the scoop paddles 289.

Mounted on the frame between the upper flight of the powder drying belt 230 and the top Wall 58 just beneath the feeder 28| is a powder spreader 305 (Figs. 3, 4, 5 and 8) which is preferably of the Jeirey-Traylor vibrating type. This spreader has a vibration producing unit 306 (Fig. 8) similar to that illustrated inyU. S. Letters Patent to E. V. Francis, No. 2,161,342, issued June 6, 1939. This unit has an armature 301 which is provided with a long, tapered, spreader deck 308, the broad end of which is located directly beneath the lower end of the pipe 296 and is surrounded on three sides by a low wall 309 (Figs.

3 and 8). Fixed on the top housing wall 58 is an arm 3|0 (Fig. 8) which extends beneath and resiliently supports the deck 308 through a coiled spring 3| Disposed below the deck 308, and rigidly secured thereto, is a powder sifter 3|5 (Figs. 5 and 8). This powder sifter is disposed horizontally about two and one-half (2l/2) inches above the powder drying belt 230. This powder sifter includes a screen 3|6 (Fig. 3) which is preferably made of fourteen (14) gauge stainless steel wire with a. mesh approximately ve-eightlis (5/8) inch square. The screen 3|6 is preferably about nine inches wider than the spreader deck 308 throughout the length of the latter so that this screen 3|6 projects four and one-half (4l/2) inches laterally beyond each of the converging edges of the deck 308.

Lying just beneath edge port .ms of the screen 3|6, and secured thereto as by brazing, is a trapezoidal shaped, reinforcing member 3|1 (Fig. 8) which is preferably made of 1/8 x 3A angle iron. This is bolted to the base of the deck 308, and adjacent its opposite end is connected to the deck by straps 320 (Figs. 3, 5 and 8). The upper surface of the deck 308 is preferably disposed approximately sixteen (16) inches above the surface of the screen 3|6 and the lowermost portions of the sifter 3|6 lie, as stated, approximately two and one-half (2l/2) inches above the upper surface of the powder drying belt 230.

It is to be understood of course that the precise measurements given are illustrative only and merely represent those -employed in a preferred embodiment of the apparatus of the invention.

The lower end of the powder pipe 296 (Figs. 4 and 8) preferably extends downwardly within the space enclosed by the three-sided wall 309 and to a level just below the upper edge of this wall. Thus, powder`is delivered from the pipe 296 to the spreader 305 and distributed in a manner to be pointed out hereinafter across the powder drier belt 230. It is to be noted here, however, that a body of powder 325 (Fig. 4) normally builds upV and is maintained in the lower end of the pipe 296 which effects a substantially air-tight seal between the drier chamber 66 and the interior of the feeder 28|.

' 'Mounted in a transverse opening 330 (Figs.v

4, '1 and 9) in the housing bottom wall portion 6| is a screw conveyor 33| which includes a trough 332 and a screw 333, the latter being formed on a shaft 334, opposite ends of which journal in bearings 335 and336. Provided on an extending end of the shaft 334 is a sprocket 331 which is connected by a chain 338 to the drive pinion sprocket 339 of a geared motor 340.

Having completed the description of the drive mechanism for driving the shafts 96, |25, |26, and 334 as Well as the beater |23 (Figs. 2 and 4), it is to be noted that this drive mechanism is excluded from the drying chamber 66 (Figs. 3 and 7). This is done by omitting the rear upper side panel 54 opposite this mechanism and forming a compartment 34| for containing this mechanism by substituting a sheet metal panel 342 (Figs. 3 and 7) for the omitted insulating panel 54, and providing an inwardly extending insulating wall 343 which completely separates the driving mechanism compartment 34| from the chamber 66.

Mounted in the lower right hand Vcorner of the drying chamber 66 so as to deflect powder delivered thereagainst into the screw conveyor."

trough 332 is a deilector 344 (Figs. 3 and 6).

l The screw conveyor operates to convey powder dropping therein towards the left hand end thereof as viewed in Figs. 7 and 9. At this' end of the conveyor, the trough 332 is provided with a discharge mouth 349 (Fig. '1).

Supported on the base 5| of the drier frame 50 is a powder cooler 350. This cooler has a long powder mixing and cooling trough 35| (Fig. 9) which is provided with a. water jacket 352 and has end walls 353 and 354 (Fig. 4). The trough 35| also has a cover 355 in which a powder inlet neck 355 is provided which connects with the conveyor discharge mouth 345. Thus, powder delivered by the conveyor 33| to its discharge mouth 345 passes downwardly through the cooler neck 355 into the right hand end of the trough 35| as this is viewed in Figs. 4 and 6. Hingedly mounted on the bottom of the cover 355 as shown in Fig. 9 is a powder valve 351 which is yieldably held upwardly by a spring 355.

Provided in the cooler end walls 353 and 354 are bearings 355 and 350 in which a heavy shaft 35| journals. This shaft is adapted to be slowly rotated by power delivered thereto through a suitable transmission 352 by a motor 353. The shaft 35| has fixed thereon powder advancing paddles 355 which, when the shaft 35| is rotated as indicated in Fig. 4, tends to advance powder delivered into the right hand end of the cooler 350 toward the left hand end thereof. At the latter end of the cooler, the shaft 35| has scoop paddles 355 and a hopper 351 (Figs. 4 and 5) which extends through the wall 353 into thespace about which the paddles 355 sweep. A guide wall 355 (Fig. 8) is also provided in said space to cause powder lifted by the scoop paddles 355 to be delivered into the hopper 351. Powder thus delivered gravitates into the lower receiving end of a screw conveyor 510 with which an airtight connection is made and which is adapted to elevate this powder and discharge it downwardly through a pipe 31| (Fig. 1) to a line of machines for packing the powder in cans under a vacuum.

The valve 351 (Fig. 9) yieldably holds upwardly and maintains in the neck 355 a mass of powder 315 so that this neck is always closed by this mass of powder against the passage of hot air downwardly from the chamber 55 through the neck 356 into the cooler 350.

The lower flight of the drier belt 230 is shown in Fig. 4 as unsupported in between the pulleys |22 and 20|. It may be preferable however to support this flight of belt 230 as by a small diameter roller 350 (Fig. rotatably mounted on the bottom housing wall portion 5|. A similar roller 354 mounted on the suction box 13l holdsthe belt 230 downward against the roller 350 and out of contact with the box 13.

It is important that the belt 230 be kept as clean as possible. This belt tends to -become impregnated with egg powder and for this reason, it is constantly cleaned by a vacuum cleaner 355 mounted in the lower housing wall section 5| and which runs continuously while the apparatus 21 is operating. If desired a rotary beater or brush may be associated with the vacuum cleaner 555 to remove adhering powder particles from the belt while the latter is subjected to the vacuum of the cleaner.

Operation The spray drier 25 and powder drier 21 are first prepared for operation by warming up certain parts of the apparatus and cooling others until the proper temperatures exist throughout. This takes about twenty minutes.

From the start of this preparation of the powder drier 21, the motors 340, |42, and |44 (Fig. 2) and the motor 29| (Fig. 7) are running; the motor 353 and blowers 255 and 255 (Fig. l2) are running; the heaters 250 and 25| and the cooler 254 arefunctioning; and the dehumidifier 12 24| (Fig. 1) is operating to dehumidify air passing therethrough.

The spreader 305 is not energized however until es! powder starts to be fed thereto by the feeder 25|. The egg powder 325 (Fig. 4) and 315 (Fig. 9) are thus maintained at the inlet and outlet powder passages of the housing 55, thereby closing these to the passage of air into or from the chamber 55 except through the air handling mechanism 240.

Before production of egg powder is started in the spray drier 25, the dew-point of the air circulated by the air system 243 is preferably below -20 F. and the temperature of this air where it leaves the risers 252 and 253 is preferably close to 220 F.

The cooler 254 is functioning to cool the air passing therethrough to a temperature of approximately 80 F.

Cooling water is supplied to the jacket 352 (Fig. 9) of the powder cooler 350 to reduce the temperature of the latter to approximately 60 F.

These values are preferred for starting but the apparatus 21 is able to maintain them throughout the running of powder.

The belt 230 is driven at one foot per minute and as the suction opening 32 is preferably five feet wide by fifteen feet long, powder delivered onto the belt by the spreader 305 (Fig. 3) is subjected to this suction opening for fteen minutes.

The spreader deck 305 is coextensive in length with the width of the suction opening 52 so that a bank B (Figs. 3, 4 and 8) of powder is generated on the belt 230 by the spreader which just overlaps the side edges of the opening 52 (Fig. 8).

The egg powder produced in the spray drier 25 has a moisture content of approximately 5% when delivered to the redrier 21 (Fig. 4). The

redrier is adapted to handle the output of this powder from the spray drier which varies from 500 lbs. to 750 lbs. per hour. When the drier 21 is handling powder at a rate within this range, the bank B of this powder is from one and onehalf to two and one-quarter inches deep.

About sixteen minutes after the delivery of powder to the spreader 305 starts, the bank B extends to the discharge end of the upper flight of the belt 230 (Fig. 4) where the powder starts dropping into the screw conveyor 33| and is delivered thereby into `the cooler 350.

The mixing and conveying shaft 35| and paddles 355 in the cooler cause the powder to progress through and be delivered from the cooler in about fifteen minutes from ,ie time it enters.

The powder in the bank B is dried as it moves over the suction opening 32, by the hot air, entering chamber 55 through the risers 252 and 253 being sucked downward through the powder bank B. the belt 230, and the apron 54 by the suction imposed upon the suction chambers ||5 and ||1 by the blowers 255 and 255 respectively. As noted, the egg powder in bank B is preferably subjected to this hot air for fifteen minutes.

A feature of the invention which contributes largely to the production of egg powder with a hitherto unattainably low moisture content, as well as an unusually low fluorescence value, is the banking of the egg powder. produced by the initial spray drying step, while applying hot air thereto to further reduce the moisture content thereof. When the powder is thus subjected to the hot air, the individual particles of powder are protected by the others surrounding it so that the cooling action produced in the individual 13 particles, by the giving up of moisture therefrom holds the temperature of the powder down, especially while the powder is still relatively moist which is the time when the powder is most susceptible to heat damage.

As the powder in mass form loses moisture, the temperature of the ypowder of course rises but in the method of this invention, the raising of the temperature of the powder in mass form is delayed with the result that the moisture content of the powder is so low, when the powder eventually does get heated up, that the elevated temperature to which the powder is then subject has no damaging effect on the powder.

The sifting of the powder, as this is spread over the belt 230 in generating the powder bank B, is another feature which contributes to the remarkable results obtained with the invention. Egg powder tends to agglomerate in lumps particularly Where the moisture content is high. The sifter 3|5 vibrates with the armature 301 of the spreader 305 (Fig. 8) and practically every lump of powder which falls downwardly thereon from the spreader deck 308 is struck by the wires of the screen 3|6 and broken up into very fine particles. In fact, the sifter 3|5 practically breaks this powder up and delivers it onto the belt 230 in the form of the separate iine particles in which the powder was originally produced in the spray drier 20.

Being sifted just above the belt 230, these ne powder particles produce a very light, fluiy bank B of egg powder which is homogeneous throughout and oiers a maximum opportunity for the air to pass therethrough in the drying operation, yet leaves no particle isolated in the air stream whereby it might be damaged by the high temperature of the latter.

Tests in representative commercial operations show that with the drying air at 220 F. and with an initial dew point of less than 20 F. the powder in the top half of the bank B reaches an equilibrium moisture of about v.45% after proceeding 9.5 ft. over the suction opening 82; and that an equilibrium moisture of .51% in the bottom half of the bank is reached at 14.5 ft. Drying egg powder with the bank method and using air at said temperature and dew point permits a reduction of the moisture content in fifteen minutes to less than .5% without elevating vthe temperature of the powder above 185 F. Normally the temperature of the powder at the discharge end of the upper flight of the belt 230 is not 'over 175 F. During the initial stages of drying the powder in the bank B. the temperature of the powder remains below 130 F. until it has travelled three feet and under 160 F. until it has travelled ve feet. From this point on, the temperature in the powder bank gradually rises to the maximum stated although it is to be noted that the moisture content of the upper half of the bank has been observed to reach an equilibrium moisture content of .45% at 9.5 ft.

It is to be noted that the drying is accomplished in two steps, in the rst of which the air is used after its having passed through other portions of the powder in the second step. When treated in the first drying step, the powder is relatively moist and the air passed through the powder has a comparatively high humidity by virtue of its already having been used once in the second drying step without having been dried in the meantime.

Double useof the air in a closed drying circuit increases the efficiency of the apparatus 21 and 14 makes possible the attainment of a lower moisture content in the powder treated with a-given air heating and dehumidiiying capacity.

In order to prevent the heat in the powder causing it to deteriorate it is advisable to cool the powder as quickly as possible to `a temperature below 100 F. This cooling must of course be accomplished without allowing the atmosphere to have access to the powder as low moisture egg powder is extremely hygroscopic and will pick up atmospheric moisture quickly. It is for this reason that the cooler Y350 is sealed oiI from the atmosphere and also has powder sealed connections with the drying housing 65 and with the discharge conveyor 310. Thus no moisture is allowed access to the cooler 350. While the powder is in this cooler, it is churned against the inner surfaces of the trough 35| which are kept cool by the water in the jacket 352. Besides thus churning the powder, the paddles 365 cause the latter to progress through the cooler. The powder is of course very thoroughly mixed in the cooler with the result that the powder, as discharged from the cooler and canned, is uniform as to moisture content and other qualities.

As a result of protecting thepowder from the heat of the drying air while the latter is removing moisture from the powder and then cooling the powder in a short time to a temperature under 100 F., the fluorescence value of the powder produced by this invention is very low.`

Cver a months period of recent operation, the average moisture content was .83% and the average uorescence value was 17. Thai; this uorescence value is low can be seen from the fact that a premium of 1 per pound was` at that time being paid by the Army on all purchases of egg powder, the fluorescence value of which was below 20.

That egg powder having a moisture content of less than 1% was then uncommon may also be seen from the fact that the Army at that time paid a premium of 1/zil per pound for egg powder with a moisture content between 1.75% and 1.5% 1 per pound for egg powder with a moisture content of 1.50% to 1.01%; and 11/2 per pound for egg powder with a moisture content of 1.00%

and under. i

For the apparatus'21 to operate efficiently, it is important that the drying belt 230 be kept in a relatively porous condition. The egg powder tends to be drawn into this belt and clog up the pores of the latter. As this belt turns downwardly at the discharge end of the upper flight thereof, most of the powder in the bank 4B, resting on this portion of the belt, drops therefrom by gravity and the beater |23 knocks practically all of the adhering powder from the belt. A few ne particles of egg powder remain on the belt, however, when it passes around the lower drive pulley |22 and the vacuum cleaner 385 is provided to remove these.

In spite of these provisions for cleaning the belt 230, it eventually gets clogged with egg powder and after about six days use, has tobe replaced with a clean belt.

The temperatures and values given hereinabove as preferable are by way of example only and it is to be understood that these may be varied considerably without departing from the spirit of the invention or the scope of the appended claims.

For instance a certain amount of the liquid whole egg is rendered insoluble in producing 5% egg powder by the spray method. The additional 

